HM Revenue and Customs (HMRC) has disciplined more than 600 staff over the past three years for inappropriately accessing people's personal data, reports the BBC.
Treasury financial secretary Jane Kennedy revealed the figures in a written House of Commons reply.
She said that in a large number of cases, HMRC staff had been sacked for wrongly accessing private data on individuals.
She revealed that 238 people were disciplined in 2005, 180 in 2006, and 192 in 2007.
Kennedy was responding to a question from Tory shadow home affairs spokesman James Brokenshire.
Kennedy said the figures demonstrated "the strength of HMRC's disciplinary procedures".
She said HMRC had a "strict policy forbidding staff to access customer records unless they have a legitimate business need".